Numbers & Units

Estimate the number of communicating civilisations in the galaxy from the seven Drake equation terms, each shown

Work out the conversion rate at each stage of a funnel and which stage loses the most people

Solve C1V1 = C2V2 for the one term of a dilution you have not measured yet

Find the output voltage of a two-resistor divider, or the second resistor needed to hit a target output

Calculate standard deviation and variance

What an amount is worth after years of inflation

Calculate tips and split bills

Work out the attractive force between two masses using Newton's law of gravitation

Work out the monthly and annual cash flow left on a rental once the mortgage, running costs and void allowance are taken out

Run a chi-square test of independence on a contingency table and see whether the difference is significant

30 related tools consolidated into one page

Work out magnification, true field of view and exit pupil for a telescope and eyepiece combination

Work out the storage slot Solidity assigns to a mapping key, a dynamic array element or a struct field, following the layout rules in the Solidity documentation

Build a quote from estimated hours and a rate, with overhead and contingency added on top

Look up the ground state electron configuration and noble gas shorthand for any element

Solve for voltage, current, resistance or power from any two of the other three

Calculate the factorial of any number

Discount future cash flows back to their value today

Convert between standard and scientific notation

Calculate markup and selling price

Work out how far, how long, or how fast something falls under gravity, from either the drop height or the fall time

Compare several improvements by cost against the value each is expected to add, and see which ones return their cost

Work out nCr and nPr for choosing r items from n, with and without repetition

Work out recession velocity, Hubble law distance and lookback time from a redshift

Build a Merkle root from a list of values and produce the proof for one leaf, hashing with keccak256 and pairing nodes left to right, duplicating the last one when a level has an odd number

Work out UK statutory interest and fixed compensation on an overdue commercial invoice, using the current Bank of England base rate as an input since it moves

Turn a percent composition into an empirical formula, and a molecular formula if the molar mass is known

Work out the series resistor an LED needs, rounded up to the nearest E12 value, with a safe power rating

Calculate nPr and nCr

The discount rate at which cash flows break even

Calculate your Body Mass Index

Work out the kinetic and gravitational potential energy of a mass, and the speed a fall from a given height would give it

Compare repairing against replacing an item by spreading each cost, plus its running cost, over its remaining life

Work out the confidence interval for a population mean from a sample

Work out the Bortle class and naked eye limiting magnitude from a sky brightness reading

Apply the EIP-55 mixed-case checksum to an Ethereum address, check whether one already has it right, and show it in lowercase and uppercase

Work out churn and retention for a period, and what that rate compounds to over a year

Solve PV = nRT for pressure, volume, moles or temperature when the other three are known

Calculate the greatest common divisor and least common multiple

Annual salary as an hourly, daily, weekly and monthly rate

Work out the logarithm of a value to any base, its natural log and log base 10, plus the antilog, with the change of base working shown

Calculate percentage increase or decrease between two numbers

Work out the momentum of two moving bodies and the outcome of a head-on collision where they stick together

Estimate 2026/27 Income Tax on rental profit in England or Northern Ireland with the 20% residential finance-cost tax reduction

Work out the Pearson correlation coefficient between two lists of numbers, and how much of the variance it explains

Convert an ERC-20 token amount to and from its raw on-chain integer for a given number of decimals, using BigInt so nothing is lost to floating point

Work out lifetime value from margin and churn, and how it compares to what it cost to acquire the customer

Solve for moles, mass, volume or concentration in a solution when the other three are known

Work out the belt length, speed ratio and driven rpm for a two pulley belt drive

Perform matrix operations

What to set aside each month to reach a target

Convert a signed integer to and from two's complement binary at 8, 16, 32 or 64 bits, and flag when a value overflows that width

Calculate compound interest

Work out the range, peak height and flight time of a launched object from its speed and angle, ignoring air resistance

Itemise residential purchase costs in England or Northern Ireland using SDLT rates in force from 1 April 2025

Fit a straight line through paired x and y values, with the slope, intercept and fit

Work out the gas a piece of calldata costs, charging 4 gas for each zero byte and 16 for each non-zero byte per EIP-2028, and the cost in gwei and ether at a given gas price

Work out a day rate from a target income, running costs and how many days a year are actually billable

Parse a chemical formula and add up its atomic weights to give the molar mass

Work out the ratio, output speed and output torque for a driver and driven gear or pulley pair

Evaluate math expressions

Return on investment, with the annualised rate

Add, subtract, multiply or divide two complex numbers, and show the modulus, argument and polar form of the result

Calculate percentages

Convert an angle between degrees, radians, gradians and revolutions, and an angular speed between rpm, rad/s, deg/s and Hz

Compare two properties side by side on net cash flow, net yield and total return, which do not always agree on which is stronger

Work out the central tendency, range and quartiles of a list of numbers

Work out the deterministic address a CREATE2 deployment gets from a deployer, salt and init code hash, and the address a plain CREATE deployment gets from a deployer and nonce

Work out cost per customer won from spend, and how many months of revenue it takes to earn that back

Work out the mass percentage each element contributes to a chemical formula

Work out the tap drill size for a metric or imperial thread at a chosen percentage of thread engagement

Generate Fibonacci sequences

Units you must sell to cover your fixed costs

Reduce a fraction to its lowest terms, showing it as a mixed number and a decimal, and the greatest common divisor used to simplify it

Calculate sale prices and savings

Combine or subtract sound levels, find a level at a distance, or read off the ratio behind a dB figure

Work out the effective rent after void periods, and what a void actually costs once lost rent and turnover costs are added together

Find z scores and the probability of landing below, above or between two values on a normal curve

Work out how many months of cash a business has left from its balance and monthly burn, with an optional assumed change to burn

Convert between molarity, molality, percent by mass and ppm for the same solution

Convert decimal degrees to and from degrees, minutes and seconds, or to a Great Britain Ordnance Survey grid reference

Solve quadratic equations (ax² + bx + c = 0)

Compare the avalanche and snowball methods across your debts

Perform fraction arithmetic

Work out the capitalisation rate from net operating income and price, and the price a target cap rate implies

Convert betting odds between decimal, fractional and American formats, with the implied probability

Work out pH, pOH, [H+] and [OH-] from any one of the four, at 25°C

Work out the initial bearing, back bearing and great circle distance between two latitude/longitude points

Check if a number is prime

What you own minus what you owe

Add or remove VAT from any amount

Work out the profit on a property flip after purchase, works, holding costs and selling costs

Work out the complement of two events and their combined and/or probability

Solve N = N0 x (1/2)^(t/T) for the remaining quantity, elapsed time, half-life or starting quantity

Factor any number into its prime factors

Estimate UK Capital Gains Tax on a disposal for England and Northern Ireland, using 2026/27 tax year rates and the annual exempt amount

Format numbers with locale-specific separators

Work out how much cash is left in a buy, refurbish, rent, refinance deal once the refinance has paid out

Work out how many responses a survey needs for a given margin of error and confidence level

Assign oxidation states to the elements in a compound using the standard fixed-value rules and charge balance

Generate random numbers in any range

Estimate years to financial independence from your savings rate, using the safe withdrawal rate to size the target pot

Calculate monthly loan payments

Work out a new rent from either a percentage rise or a target market rent, and the monthly and annual difference it makes

Work out the variance and standard deviation of a list of numbers, as a sample or a population

Balance a chemical equation and show the whole-number coefficients on each side

Perform advanced math operations

Estimate the maximum mortgage you could borrow from income and outgoings, and what that means for property price

Simplify ratios to their simplest form

Work out the share of the year a rental needs to be let just to cover its fixed and variable costs

Work out how many standard deviations a value sits from the mean, and its percentile

Work out moles, the limiting reagent and theoretical yield for a reaction from two reactant masses

Calculate mean, median, mode, min, max, and sum

See how much interest a regular monthly overpayment saves on a repayment mortgage, and how many years it cuts off the term

Compare the net cost of renting against buying over a chosen period, weighing mortgage payments and running costs against rent and property growth

Work out gross yield, net yield and cap rate for a rental property from its price, rent and running costs

Project a pension or savings pot at retirement from regular contributions, and what it might draw down to each year

Estimate residential Stamp Duty Land Tax in England or Northern Ireland using rates in force from 1 April 2025

See the true cost of a foreign currency purchase once the exchange margin and any flat fee are added to the mid-market rate

Work out how many months of cover your current savings provide, and what a monthly contribution would take to close the gap

Project the future value of a lump sum plus regular contributions, compounded at a frequency you choose

Compare two loans on total cost, including fees, rather than on the headline interest rate alone

Calculate appliance energy use and cost from wattage and daily run time

Estimate brute-force attempts and time for a hexadecimal address prefix

Total added hours and cost from out-of-scope change requests

Evaluate a safe arithmetic expression over an x range and return plot-ready points

Approximate one-dimensional heat diffusion with an explicit finite-difference grid

Find the cost break-even point and lifetime saving for a reusable item

Project investment growth with regular monthly contributions and an assumed return

Calculate trade gain, return percentage and break-even price including fees

Allocate income across named envelopes and show unassigned money